Conclusive studies as to the molecular composition of nerve growth factor, NGF, in snake venom will be carried out. Snake venom NGF (SV NGF) will be purified to homogeneity and its quaternary structure investigated. A detailed comparison of SV NGF vs. mouse NGF will then be carried out. Physical parameters of SV NGF such as molecular weight and isoelectric point will be determined. The biological active site of the mouse NGF Beta subunit will be subjected to extensive chemical modification for the purpose of determining the role played by specific residues in nerve growth stimulation and recombination into the multimer form. In addition, the Beta subunit tyrosine residues will be radioactively labelled in vitro with I125 and the lysine residues with C14 in order to characterize and isolate the cellular receptor of NGF. Finally the protein composition of NGF sensitive 14 day old chick dorsal root ganglia will be compared with the NGF insensitive 16 day old chick dorsal root ganglia.